Open phase detection

Abstract

An example transformer includes a controller that determines the currents on a power grid side of the transformer, as well as an inverter/load side of the transformer. The transformer may be of a delta-wye configuration. The controller compares the currents on the delta side of the transformer to the currents on the wye side of the transformer to determine whether the currents on either side are imbalanced. If the currents on the delta side are balanced, while the currents on the wye side are imbalanced, then the controller may determine that an open phase condition exists on the wye side of the transformer. Alternatively, if the currents on the delta side are imbalanced or if the currents on the delta side are balanced and the currents on the wye side are also balanced, then the controller determines that no open phase condition exists.

What is claimed is: 
     
       1. A method of detecting an open phase condition, comprising:
 measuring, using one or more meters, a first current value, a second current value, and a third current value associated with a first side of a transformer; 
 measuring, using the one or more meters, a fourth current value, a fifth current value, and a sixth current value associated with a second side of the transformer; 
 determining, by a controller, that the first current value, the second current value, and the third current value are imbalanced by determining that one of the first current value, the second current value, or the third current value is greater than a threshold value different from the other two of the first current value, the second current value, or the third current value; 
 determining, by the controller, that the fourth current value, the fifth current value, and the sixth current value are balanced; 
 determining, by the controller and based at least in part on first current value, the second current value, and the third current value being imbalanced and the fourth current value, the fifth current value, and the sixth current value being balanced, that an open phase condition exists on the first side of the transformer; and 
 disconnecting, by the controller and based at least in part on determining that the open phase condition exists, the transformer from a power grid or an inverter by actuating a relay or connector switch. 
 
     
     
       2. The method of  claim 1 , wherein the first side of the transformer is a power grid side of the transformer and the second side of the transformer is an inverter/load side of the transformer. 
     
     
       3. The method of  claim 1 , wherein the first side of the transformer includes a wye winding and the second side of the transformer includes a delta winding coupled to the wye winding. 
     
     
       4. The method of  claim 1 , wherein the first current value is associated with a first phase of a power grid, the second current value is associated with a second phase of the power grid, and the third current value is associated with a third phase of the power grid. 
     
     
       5. The method of  claim 1 , further comprising:
 indicating, based at least in part on determining that the open phase condition exists on the first side of the transformer, that the open phase condition has been detected. 
 
     
     
       6. The method of  claim 1 , wherein determining that the first current value, the second current value, and the third current value are imbalanced further comprises:
 determining that one of the first current value, the second current value, or the third current value is substantially zero, while the other two of the first current value, the second current value, or the third current value are substantially non-zero. 
 
     
     
       7. The method of  claim 1 , wherein determining that the fourth current value, the fifth current value, and the sixth current value are balanced further comprises:
 determining that each of the fourth current value, the fifth current value, and the sixth current value are within the threshold value of each other. 
 
     
     
       8. The method of  claim 1 , further comprising:
 sending, by the controller and to an electronic device, a notification to indicate the open phase condition. 
 
     
     
       9. A system, comprising:
 one or more meters; 
 a transformer having a power grid side and an inverter/load side; and 
 a controller configured to:
 measure, using the one or more meters, a first current value, a second current value, and a third current value associated with power grid side of the transformer; 
 measure, using the one or more meters, a fourth current value, a fifth current value, and a sixth current value associated with inverter/load side of the transformer; 
 determine that the first current value, the second current value, and the third current value are imbalanced by determining that one of the first current value, the second current value, or the third current value is greater than a threshold value different from the other two of the first current value, the second current value, or the third current value; 
 determine that the fourth current value, the fifth current value, and the sixth current value are balanced; 
 determine, based at least in part on first current value, the second current value, and the third current value being imbalanced and the fourth current value, the fifth current value, and the sixth current value being balanced, that an open phase condition exists on the power grid side of the transformer; and 
 disconnect, based at least in part on the open phase condition, the transformer from a power grid or an inverter from the transformer. 
 
 
     
     
       10. The system of  claim 9 , further comprising:
 a wye winding on the power grid side of the transformer; and 
 a delta winding on the inverter/load side of the transformer. 
 
     
     
       11. The system of  claim 9 , wherein the controller is further configured to:
 indicate, based at least in part on determining that the open phase condition exists on the power grid side of the transformer, that the open phase condition has been detected. 
 
     
     
       12. The system of  claim 9 , wherein to determine that the first current value, the second current value, and the third current value are imbalanced, the controller is further configured to:
 determine that one of the first current value, the second current value, or the third current value is substantially zero, while the other two of the first current value, the second current value, or the third current value are substantially non-zero. 
 
     
     
       13. The system of  claim 9 ,
 wherein the controller is further configured to: 
 receive, from the one or more meters, the fourth current value, the fifth current value, and the sixth current value. 
 
     
     
       14. The system of  claim 9 , wherein the controller is further configured to:
 measure, at a second time and using the one or more meters, the first current value, the second current value, and the third current value associated with power grid side of the transformer; and 
 determine, at the second time, that the that the transformer is operating without an open phase condition at the second time. 
 
     
     
       15. A system, comprising:
 one or more meters; 
 a transformer having a wye side and a delta side; and 
 a controller configured to:
 determine, using the one or more meters and at a first time, a first current value of a first phase on the wye side, a second current value of a second phase on the wye side, and a third current value of a third phase on the wye side; 
 determine, using the one or more meters and at the first time, a fourth current value of the first phase on the delta side, a fifth current value of the second phase on the delta side, and a sixth current value of the third phase on the delta side; 
 determine that the first current value, the second current value, and the third current value are imbalanced by determining that one of the first current value, the second current value, or the third current value is greater than a threshold value different from the other two of the first current value, the second current value, or the third current value; 
 determine, using the one or more meters, that the fourth current value, the fifth current value, and the sixth current value are imbalanced; and 
 determine, based at least in part on first current value, the second current value, and the third current value being imbalanced and the fourth current value, the fifth current value, and the sixth current value being imbalanced, that the transformer is operating without an open phase condition at the first time. 
 
 
     
     
       16. The system of  claim 15 , wherein the controller is further configured to:
 determine, at a second time, a seventh current value of the first phase on the wye side, an eighth current value of the second phase on the wye side, and a ninth current value of the third phase on the wye side; 
 determine, at the second time, a tenth current value of the first phase on the delta side, an eleventh current value of the second phase on the delta side, and a twelfth current value of the third phase on the delta side; 
 determine that the seventh current value, the eighth current value, and the ninth current value are imbalanced; 
 determine that the tenth current value, the eleventh current value, and the twelfth current value are balanced; and 
 determine, based at least in part on seventh current value, the eighth current value, and the ninth current value being imbalanced and the tenth current value, the eleventh current value, and the twelfth current value being balanced, that an open phase condition exists on a power grid side of the transformer at the second time. 
 
     
     
       17. The system of  claim 16 , wherein the controller is further configured to:
 indicate, based at least in part on determining that the open phase condition exists on the power grid side of the transformer at the second time, that an open phase condition has been detected. 
 
     
     
       18. The system of  claim 16 , determine that one of the seventh current value, the eighth current value, or the ninth current value is greater than a threshold value different from the other two of the seventh current value, the eighth current value, or the ninth current value. 
     
     
       19. The system of  claim 16 , wherein the controller is further configured to:
 disconnect, based at least in part on determining that the open phase condition exists at the second time, the transformer from a power grid or an inverter from the transformer. 
 
     
     
       20. The system of  claim 15 , wherein the wye side of the transformer is a power grid side of the transformer and the delta side of the transformer is an load side of the transformer.